Condition monitoring apparatus for wind turbine

Abstract

Frequency analysis units are configured to perform a frequency analysis of vibrations detected by vibration sensors, respectively. A natural frequency detection unit is configured to detect a natural frequency of a wind turbine in accordance with a direction of a nacelle, based on results of the frequency analysis. A change ratio calculation unit calculates a decrease ratio in the natural frequency detected by the natural frequency detection unit. An abnormality detection unit determines that an abnormality is present in the wind turbine if the decrease ratio in the natural frequency calculated by the change ratio calculation unit exceeds a threshold value.

The invention claimed is: 
     
       1. A condition monitoring apparatus for a wind turbine, the wind turbine having a nacelle rotatably supported on a support, the condition monitoring apparatus comprising:
 a vibration detection unit configured to detect a vibration generated in the wind turbine; 
 a frequency analysis unit configured to perform a frequency analysis of the vibration detected by the vibration detection unit; 
 a natural frequency detection unit configured to detect a natural frequency of the wind turbine in accordance with a direction of the nacelle, based on a result of the frequency analysis; and 
 an abnormality detection unit configured to detect whether or not an abnormality is present in the wind turbine, based on the natural frequency detected by the natural frequency detection unit. 
 
     
     
       2. The condition monitoring apparatus for the wind turbine according to  claim 1 ,
 wherein 
 the direction of the nacelle is divided into a plurality of sections, 
 the natural frequency detection unit is configured to detect the natural frequency for each of the plurality of sections, based on the result of the frequency analysis, and 
 the abnormality detection unit is configured to detect an abnormality of the wind turbine if a decrease ratio in the natural frequency from the beginning of installation of the wind turbine in any of the plurality of sections exceeds a prescribed value. 
 
     
     
       3. The condition monitoring apparatus for the wind turbine according to  claim 1 , wherein
 the natural frequency detection unit is configured to detect at least six different natural frequencies for each of a plurality of sections of the direction of the nacelle. 
 
     
     
       4. The condition monitoring apparatus for the wind turbine according to  claim 1 , wherein
 the natural frequency detection unit is configured to detect the natural frequency when a prescribed environmental condition lasts for a predetermined duration. 
 
     
     
       5. The condition monitoring apparatus for the wind turbine according to  claim 1 , wherein
 the frequency analysis unit is configured to perform the frequency analysis by executing a Fourier transform on a waveform of the vibration detected by the vibration detection unit, and 
 a time length on a time base of the waveform on which the Fourier transform is to be executed is 300 seconds or greater. 
 
     
     
       6. The condition monitoring apparatus for the wind turbine according to  claim 1 , wherein
 the vibration detection unit includes a plurality of vibration sensors. 
 
     
     
       7. The condition monitoring apparatus for the wind turbine according to  claim 6 , wherein
 the natural frequency detection unit is configured to identify a vibration mode of the wind turbine, based on a result of comparison between a phase of a spectrum of a vibration detected by a first vibration sensor of the plurality of vibration sensors and a phase of a spectrum of a vibration detected by a second vibration sensor of the plurality of vibration sensors. 
 
     
     
       8. The condition monitoring apparatus for the wind turbine according to  claim 7 , wherein
 the first vibration sensor is provided on a more forward side of the nacelle than a rotation shaft of the nacelle with respect to the support, and 
 the second vibration sensor is provided on a more rear side of the nacelle than the rotation shaft. 
 
     
     
       9. The condition monitoring apparatus for the wind turbine according to  claim 1 , wherein
 the wind turbine includes a rotation vibration detection unit configured to detect a vibration of a rotary device rotating with rotation of blades receiving a wind force, and 
 the vibration detection unit is configured to detect a vibration with a frequency lower than a frequency detected by the rotation vibration detection unit.